1. Field of the Invention
The present invention relates to an element substrate, a printhead, and a printing apparatus and, particularly, to a full-line printhead having an element substrate integrated with it, which performs printing in accordance with, for example, an inkjet method and a printing apparatus that performs printing using the same. More specifically, the present invention relates to a printhead including an element substrate, in which a plurality of print elements and driving circuits configured to drive the print elements are provided on the single element substrate, and a printing apparatus.
2. Description of the Related Art
For example, as information output apparatuses such as a word processor, a personal computer, and a facsimile apparatus, in general, inkjet printing apparatuses (to be referred to as printing apparatuses hereinafter) for printing any desired information such as characters and images on a sheet-like printing medium such as a paper sheet or a film are widely used.
Electrothermal transducers (heaters) of a printhead included in a printing apparatus and driving circuits thereof are generally formed on a single substrate using the semiconductor process technology as described in, for example, Japanese Patent Laid-Open No. 2007-022069. As one configuration, there is proposed a printhead having an element substrate integrated with it, in which an ink supply port is located near the center of the substrate, and heaters facing each other are located at positions sandwiching the ink supply port.
In addition, for example, Japanese Patent Laid-Open No. 10-119273 discloses a method of correcting a fluctuation in the discharge characteristics of a printhead with respect to the temperature.
FIG. 22 is a timing chart showing the structure of a double-pulse.
As shown in FIG. 22, in a double-pulse, a preheat signal (prepulse) to a printhead is generated before the discharge timing of a main pulse, and an interval time is generated between the main pulse and the prepulse. In the times of these pulses, temperature correction of the printhead, correction by a fluctuation in the sensitivity of a temperature sensor, correction by a fluctuation in the temperature-discharge characteristics of each nozzle, and the like are reflected. Note that the pulse width of the prepulse, the interval time, and the pulse width of the main pulse are represented by T1, T2, and T3, respectively, and the same reference symbols are used throughout the following explanation.
For example, Japanese Patent Laid-Open No. 2008-302691 discloses an arrangement that adjusts the respective times of a double-pulse in accordance with the environmental temperature.
FIGS. 23A and 23B are views showing an example in which the respective times of a double-pulse are adjusted in accordance with the environmental temperature based on the arrangement disclosed in Japanese Patent Laid-Open No. 2008-302691.
According to FIG. 23A, for example, when the environmental temperature envT is 28° C. or more, PWM4 is selected as a driving pulse. In this case, as shown in FIG. 23B, the start time of the pulse delays as compared to the remaining three pulses PWM1 to PWM3. However, the total time of the double-pulse is constant in principle. In particular, the fall of the main pulse is constant to align the discharge timing.
When the arrangement of the above-described related art is employed, the pulse width of an HE signal can desirably be set. However, in a case where a heater is driven a plurality of times at the same heating period, that is, an HE signal pulse is given a plurality of times, as shown in FIG. 22, reference voltage setting data corresponding to the plurality of pulse times is necessary, and the amount of data increases. As a result, a countermeasure need to be taken by, for example, increasing the speed of data transfer from the main body of the printing apparatus to the printhead or dividing data. This poses problems such as a decrease in reliability of a print operation and an increase in the number of terminals on the element substrate of the printhead. Additionally, the circuit scale increases because a plurality of memories are needed to set a plurality of pulse width data.